CN109881696B - HPPG (high Performance Poly propylene glycol) bottom sealing construction method - Google Patents
HPPG (high Performance Poly propylene glycol) bottom sealing construction method Download PDFInfo
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- CN109881696B CN109881696B CN201910100642.1A CN201910100642A CN109881696B CN 109881696 B CN109881696 B CN 109881696B CN 201910100642 A CN201910100642 A CN 201910100642A CN 109881696 B CN109881696 B CN 109881696B
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Abstract
The invention relates to a HPPG back cover construction method, which comprises the following steps: a) determining a deeper back cover construction depth according to the depth of the designed foundation pit; b) determining that the design diameter D of the consolidated body at the construction depth of the back cover is not less than 600 mm; c) determining the arrangement distribution of the consolidation bodies on the back cover construction depth plane, and forming a generally close-packed hexagonal or quincunx array which is mutually occluded with each other; d) punching the bottom layer according to the determined arrangement distribution of the consolidated bodies until the construction depth of the back cover; e) at the bottom sealing construction depth, carrying out rotary spraying on the stratum by using compressed air and high-pressure cement slurry to form mixed cement slurry of cement slurry and soil slurry with the diameter not less than D; f) the mixed slurry body is solidified into a cement concretion body with the height not less than 100 cm and the compressive strength not less than 1.0 MPa. The consolidated body can achieve the effects of sealing bottom and preventing water from flowing as long as the consolidated body can achieve the arrangement, the size and the strength.
Description
Technical Field
The invention relates to a method for strengthening and sealing off a bottom working surface under the influence of underground water.
Background
In the underground engineering construction process, for example: in order to control underground water, a suspension type curtain and water pumping in a pit (a cave) are an effective method at present. Under the condition that the condition allows, can reduce the engineering cost by the type curtain that falls to the bottom significantly. In some cases, however, a series of engineering problems can arise under the influence of groundwater, due to improper treatment of the bottom working surface.
Engineering problems arising under the above conditions can be broadly divided into two broad categories, depending on the location of the bottom working surface and aquifer. The bottom working surface is located in the water-containing layer: the effective water barrier is not squeezed into to the waterproof curtain, and the mutual UNICOM of hole (hole) inside and outside aquifer (dive or confined water) can cause the water waste when carrying out hole (hole) interior pumping, causes ground subsides simultaneously, causes the influence to the surrounding environment. The bottom working surface is positioned on the upper part of the aquifer: the waterproof curtain is not punched into an effective waterproof layer, the inner and outer aquifers of the pit (hole) are communicated, along with the process of pumping water and excavating in the pit (hole), the bottom working face can generate the phenomena of gushing of confined water, bottom uplift, gushing of water and sand due to the pressure of the confined water below. The schematic of the two cases is shown in fig. 1.
The current methods for treating the problems comprise three common treatment methods of waterproof curtain partition, deep well precipitation decompression and bottom sealing. The waterproof curtain is separated by arranging the waterproof curtain at the periphery of the foundation pit, the bottom of the waterproof curtain enters the effective waterproof layer to play a role in stopping water, but when the effective waterproof layer is buried deeply, the height of the waterproof curtain is greatly increased, and the manufacturing cost is obviously increased. The deep well dewatering decompression is that the dewatering decompression well is driven into the pressure water layer to reduce the height of the pressure water head of the basement, but the use is limited in the actual engineering due to the site, and the ground settlement and the waste of underground water resources are caused by pumping and draining the underground water. The bottom sealing is realized by injecting grouting at the bottom of the foundation pit, so that the effects of reinforcing the foundation pit bottom plate and stopping water are achieved. The method for sealing the bottom comprises the following steps: a. adopting a high-pressure rotary jet grouting method to manufacture a waterproof bottom plate integrated with a curtain structure around the pit below the bottom surface of the foundation pit before excavation; b. adopting a grouting method or a high-pressure rotary jet grouting method to manufacture a waterproof bottom plate integrated with a pit peripheral curtain structure before excavation; c. and (3) adopting a freezing method, and manufacturing a waterproof bottom plate integrated with a curtain structure around the pit below the bottom surface of the foundation pit before excavation.
Disclosure of Invention
The method aims to reinforce the base by performing high-pressure rotary spraying and double-liquid grouting on the bottom of the working face, prevent the bottom of the working face from water seepage and sand gushing, and is suitable for projects such as foundation pits, tunnels and the like constructed by various open excavation, underground excavation and shallow-buried underground excavation methods (side-hole method, middle-hole method and hole-pile method), and under the condition that the projects are influenced by underground water and need to be bottomed.
Therefore, the invention provides an HPPG back cover construction method, which comprises the following steps:
a) determining a deeper back cover construction depth according to the depth of the designed foundation pit;
b) determining that the design diameter D of the consolidated body at the construction depth of the back cover is not less than 600 mm;
c) determining the arrangement distribution of the consolidation bodies on the back cover construction depth plane, and forming a generally close-packed hexagonal or quincunx array which is mutually occluded with each other;
d) punching the bottom layer according to the determined arrangement distribution of the consolidated bodies until the construction depth of the back cover;
e) at the bottom sealing construction depth, carrying out rotary spraying on the stratum by using compressed air and high-pressure cement slurry to form mixed cement slurry of cement slurry and soil slurry with the diameter not less than D;
f) the mixed slurry body is solidified into a cement concretion body with the height not less than 100 cm and the compressive strength not less than 1.0 MPa.
The consolidated body can achieve the effects of sealing bottom and preventing water from flowing as long as the consolidated body can achieve the arrangement, the size and the strength.
Preferably, in step e), high pressure air is simultaneously swirled. Therefore, the working efficiency can be improved, and a solidified body with larger size or uniform material can be obtained.
Preferably, in the step e), the pressure of the cement slurry is not less than 0.2MPa, the specific gravity of the slurry is 1.60-1.80 ton/m 3, the pressure of compressed air is not less than 0.5MPa, and the pressure of high-pressure water is not less than 30 MPa. Of course, higher water pressure results in higher operating efficiency.
Preferably, in the step e), the specific gravity of the slurry is 1.60-1.80, the pressure of the slurry is not less than 20MPa, and the pressure of the compressed air is not less than 0.7 MPa. And the slurry pressure is higher in operation efficiency.
Preferably, in the step e), the rotary spraying rotating speed is not less than 20 r/min.
Preferably, in step e), the centers of three adjacent concretion bodies form the vertex of a regular triangle, and the side length of the regular triangle is 0.7-0.8D. Therefore, the adjacent consolidation bodies can be combined and fastened, and the filling material is relatively saved while the efficiency is improved.
Preferably, in step e), D is equal to 800mm and the sides of the regular triangle are 600 mm.
Preferably, the grouting finishing standard is as follows: and when the grouting amount is less than 20 liters/min, continuously stabilizing for 15min after the reading of the pressure gauge is stabilized to be more than 2.5Mpa, and ending the step e). This gives consideration to the filling degree and the construction efficiency of grouting, and simultaneously, the pump is not held back.
Drawings
FIG. 1 two common problems with water pumping in a hanging curtain + pit (hole);
FIG. 2 shows three methods of high-pressure jet grouting;
FIG. 3 is a geological profile of a construction site;
FIG. 4 is a schematic view of the bottom sealing and reinforcing in the construction site;
FIG. 5 is a schematic diagram of a hole site of a jet grouting pile;
FIG. 6 is a flow chart of construction of a jet grouting pile;
FIG. 7 is a schematic view of a grout hole arrangement;
FIG. 8 is a grouting construction flow chart;
fig. 9 shows a layout of a grouting system.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
Before the HPPG back cover construction method is introduced, certain explanation is firstly carried out on the HPPG:
h means high, P means pressure, P means pile, and G means grounting, wherein HP means high pressure, and PG means pile + grouting. HPPG is the abbreviation of high pressure rotation grouping pile and grouping, namely high pressure jet grouting and grouting.
The bottom sealing construction technology of the invention is successfully applied to the construction of subway stations in a certain city, thereby saving valuable underground water resources and realizing immeasurable social and economic values. In addition, the successful implementation of the back cover construction technology avoids the ground settlement deformation in a large range around the station, prevents the cracking, the inclination and the sinking of the surrounding road surface, underground pipelines and buildings (structures), ensures the normal life of surrounding residents and creates good social benefits. The gist of this embodiment is as follows:
1. the high-pressure jet grouting method for the high-pressure jet grouting pile is characterized in that a drilling machine is used for drilling a grouting pipe with a nozzle into a preset position of a soil layer, then high-pressure equipment is used for enabling slurry or water and even air to be high-pressure jet flow of 20-40 MPa (the upper limit is limited by the economic and technical performance of the existing pump), the high-pressure jet grouting pile is ejected from the nozzle, a soil body is punched, disturbed and damaged, meanwhile, a drill rod is gradually lifted at a certain speed, the slurry and soil particles are forcibly stirred and mixed, and after the mixed slurry is solidified, a cylindrical solidification body (namely the jet grouting pile) is formed in the soil, so that the purposes of foundation reinforcement or water and seepage prevention are achieved. Depending on the injection method, there are classified into a single tube method, a double tube method and a triple tube method.
The single-tube method comprises the following steps: single layer jet pipe, only jet cement slurry. The double-tube method comprises the following steps: the double-grouting pipe is used to transversely jet two medium jets, namely high-pressure cement slurry and air, to impact and damage soil. Under the combined action of the high-pressure slurry and the surrounding airflow of the outer ring, the energy for destroying the soil body is obviously increased, and finally, a larger consolidation body is formed in the soil. Triple tube method: the method is characterized in that a triple grouting pipe for respectively conveying three media of water, gas and grout is used, a cylindrical airflow surrounds the periphery of high-pressure water flow generated by a high-pressure generating device such as a high-pressure pump, high-pressure water flow jet flow and airflow are coaxially jetted to punch and cut a soil body to form a larger gap, then grout is injected into a cut and broken foundation by a slurry pump at a lower pressure, a nozzle rotates and lifts to mix the grout with soil and solidify the grout in the soil to form a larger solidified body, and the diameter of the solidified body can reach 2 m. Schematic diagrams of the three grouting processes are shown in fig. 2.
The pile forming diameter required in the project is 800 mm. The triple pipe method has good pile forming quality and high efficiency, and is mainly selected as a pile forming means by combining the stratum conditions of the project; the single-tube method and the double-tube method are also used under conditions that can meet design requirements. The three recommended technical parameters are as follows:
(1) single-double tube method: the slurry pressure is 20-40 MPa (the upper limit is limited by the economic and technical performance of the existing pump), the slurry proportion is 1.30-1.49, the rotary spraying speed is 20r/min, the lifting speed is 0.2-0.25 m/min, the nozzle diameter is 2-3 mm, and the slurry flow rate is 80-100L/min (the flow rate can be increased according to the pile diameter).
(2) The double-tube method comprises the following steps: the pressure of the slurry is 20-40 MPa, and the pressure of the compressed air is 0.7-0.8 MPa.
(3) Triple tube method: the slurry pressure is 0.2-0.8 MPa (the upper limit is limited by the economic and technical performance of the existing pump), the slurry specific gravity is 1.60-1.80, the compressed air pressure is 0.5-0.8 MPa, and the high-pressure water pressure is 30-50 MPa (the upper limit is limited by the economic and technical performance of the existing pump).
2. The double-liquid grouting is that the grout is pressed into the stratum through a grouting pipe by external acting force such as hydraulic pressure, air pressure or other methods, water and air in the soil body are discharged, and the grout is filled; the slurry is utilized to solidify and bond the soil body into a whole, thereby improving the physical and mechanical properties of the injected soil layer, improving the strength and stability of the soil body, and reducing the permeability, so as to achieve the engineering purpose of reinforcing or plugging water.
Grouting materials are one of the key factors of grouting engineering. The types of the grouting materials can be classified into two main types after being summarized: solution type and suspension type. The solution type grouting material is also called chemical grouting material and is divided into water glass, lignin, acrylamide, acrylate, polyurethane, epoxy resin, methacrylate, urea resin and other chemical grouting materials. The suspension type grouting material is a material in which solid particles in grout are suspended in water, and mainly comprises cement paste, cement clay paste, cement water glass paste and the like. The chemical slurry is mainly composed of organic chemicals and generally has the characteristics of small initial viscosity, adjustable gel time, controllable grouting range and the like. However, such slurries are expensive, have low strength and poor durability, tend to be toxic, and have harsh application conditions. In suspension type grouting materials, the application range of cement slurry is the widest, and the cement slurry has the advantages of high strength, good impermeability, wide material source, no toxicity, no pollution and the like, but the cement slurry has the defects of long gelling time, poor stability, reduced later-period performance and the like, so the cement slurry is often used together with other additives. In recent years, with the development of grouting materials, ultrafine cement, nano cement, high water-fast setting materials, acidic water glass slurry materials, high molecular chemical materials and the like are gradually applied to grouting engineering, and good effects are obtained.
The material that double-liquid slip casting adopted in this embodiment is water glass + cement. The slurry is widely used in engineering due to low cost, convenient material taking and environmental protection. In addition to the slurry material used in the present engineering, other slurries can be considered for use when the design requirements are met and the conditions such as price are reasonable.
More specifically, the subway station is preliminarily designed into a suspended curtain plus a pit internal precipitation, and then the normal excavation of a foundation pit is realized. However, in the exploration depth range, the underground water level is 782.76-789.55 m, the water level burial depth is 1.6-5.7 m, and the water level needs to be lowered by more than 16 m. Because the subway station is positioned in an old urban area, the street is narrow, and the residential building close to the foundation pit of the station has high survival rate and dense population, old pipelines such as tap water, rain sewage, heat, coal gas and the like around the foundation pit can not be moved outside the construction influence range of the foundation pit under the limitation of the site. The early-stage precipitation test shows that the house settlement caused by precipitation is large, so the large-range precipitation condition cannot be met, if precipitation is continued, the settlement caused by precipitation can cause pipeline damage and even breakage, serious consequences such as foundation pit peripheral ground collapse and resident panic occur, the economic loss is huge, and the occurrence of dangerous cases causes severe social influence. If the excavation is carried out without precipitation, the confined water head is higher, once large gushing water and sand gushes occur in the pit, the pipeline can be damaged or even broken, the damage is catastrophic, and the social influence is huge due to the dangerous case. The geological profile and the back cover area of this embodiment are shown in fig. 3.
The length of the station is 258m, the width of the station is 22.1m, the total height of the station is 13.39m, and the buried depth of the structural bottom plate is about 16.14-16.98 m. The width of the small-range shield end head section is 32.5m, the width of the large-range shield end head is 28.8m, the total height is 14.72m, and the buried depth of the bottom plate is about 17.87-18.03 m. The station main body is an underground double-layer island type station, the structural form is a double-column three-span (locally adopting a single-column double-span) cast-in-place frame structure, and the underground water control mode is a method of underground continuous wall suspension type curtain, pit internal precipitation and bottom sealing. The back cover of the station is shown in figure 4.
The specific construction process of the high-pressure jet grouting pile and the double-liquid grouting in the embodiment is as follows:
1. the height of the triple-tube rotary spraying pile of the high-pressure rotary spraying pile is 2.5-7.5 m below the substrate.
(1) Material and apparatus
1) Materials: P.O 42.5.5 Portland cement;
2) drilling equipment: a rotary jet grouting pile machine, an air compressor, a high-pressure pump and a grouting pump;
3) grouting equipment: a matched grouting pipe;
4) pulping equipment: a cement stirring barrel and a stirrer;
5) auxiliary equipment: flow meters, slurry densitometers, and the like.
(2) Construction process flow
1) The working face is arranged on the excavated part of the earthwork, and C15 concrete with the thickness of 20cm is poured to serve as a grouting working platform.
2) And (4) arranging pile positions on the spot according to a drawing of the hole position arrangement of the drawing by using a steel ruler and a measuring line, nailing tightly by using bamboo sticks, and ensuring that the displacement deviation of the center of a pile hole is less than 20mm by using one pile. The high-pressure jet grouting piles are arranged in a 600mm x 600mm quincunx or close-packed hexagonal mode, as shown in figure 5.
3) The drilling machine positions and moves the rotary jet grouting pile machine to a designated pile position, the drill bit is aligned to the center of the hole position, the drilling machine is placed horizontally, stability and horizontality are kept, and the verticality deviation of the drill rod is not more than 1%. After the nozzle is in place, a low-pressure (0.5MPa) water injection test is firstly carried out to check whether the nozzle is unblocked and whether the pressure is normal.
4) When the pile machine is shifted during slurry preparation, cement slurry is mixed according to the designed mixing ratio, P.O 42.5.5 type common Portland cement is used as the material, a proper amount of additives are added according to the requirement, the amount of the used additives is determined by tests according to specific conditions, the water cement ratio of the cement slurry is about 1.0, the cement mixing amount is about 35%, and the compressive strength of cement soil is not lower than 1.0 MPa. Firstly, adding water into a barrel, pouring cement and an admixture into the barrel, starting a stirrer to stir for 10-20 minutes, and detecting the specific gravity of the slurry. And (3) unscrewing a valve at the bottom of the stirring barrel after meeting the requirement, putting a first screen (the aperture is 0.8mm), filtering, flowing into a slurry pool, pumping a second screen (the aperture is 0.8mm) through a slurry pump, filtering for the second time, flowing into the slurry barrel, and pressing for later use.
5) The purpose of hole-forming construction drilling is to smoothly place a grouting pipe into a preset position, and the grouting pipe is generally used as a drill rod for drilling. In the pipe descending process, if a drilling machine cannot open holes due to the fact that certain obstacles such as boulders, concrete pavements, miscellaneous fill hard objects and the like are encountered, a high-hardness alloy drill bit is adopted for guiding holes firstly. When drilling, the nozzle is prevented from being blocked by mud and sand outside the pipe, the pipe is smoothly lowered, and compressed air flow is conveyed simultaneously in the pipe lowering process until the grouting spray head is lowered to a preset position (designed pile bottom). The deviation of the position of the drilled hole from the design position must not be greater than 50 mm.
6) High-pressure jet pile
Test tube
And when the grouting pipe is placed into the soil layer to a preset depth, the grouting pipe is tested by using clear water, and if the grouting equipment and the high-pressure pipeline are safe and normal, cement slurry can be stirred and manufactured to start high-pressure grouting operation.
And secondly, constructing by a triple pipe method of jet grouting, wherein after the designed depth is reached, a high-pressure water pipe and an air pressure pipe are connected, a high-pressure clean water pump, a slurry pump, an air compressor and a drilling machine are started to rotate, pressure, flow and air quantity are controlled by instruments, lifting is started when the preset values are respectively reached, rotary spraying and lifting are continued until the preset reinforcement height is reached, and then the construction is stopped. The construction parameters are shown in table 1.
And thirdly, when the rotary spraying pipe is lifted to be close to the pile top, the pile head is lifted and sprayed at a low speed from 1.0m below the pile top for several seconds, and then lifted upwards at a low speed for 0.5m until the pile top stops grouting. The top of the spray-stopping pile is about 0.5m higher than the designed pile top, and the position of the pile bottom is about 0.5m lower than the designed pile bottom. If meeting gravel stratum, in order to ensure pile diameter, repeatedly spraying and stirring according to the above steps until the spraying pipe is lifted to a grout stop surface, closing a high-pressure slurry pump (a clean water pump and an air compressor), stopping conveying cement grout (water and air), rotatably lifting the rotary spraying pipe out of the ground, and closing a drilling machine.
7) After the construction of flushing and shifting and jetting of the drilling machine is finished, machines such as a grouting pipe and the like are flushed clean, no cement paste can remain in the pipe and the machine, and the slurry is generally changed into water and jetted on the ground so as to completely remove the slurry in a slurry pump, the grouting pipe and a hose. And moving the machine tools such as a drilling machine and the like to the new hole position.
8) After the grouting operation is completed, due to the water separation effect of the grout, the grout generally shrinks in different degrees, so that a recess appears at the top of the consolidation body, and the grout with the water cement ratio of 1.0 needs to be used for grouting in time.
The technological process of triple-pipe rotary jet grouting pile construction in bottom sealing construction is shown in figure 6.
TABLE 1 concrete construction parameters of high-pressure jet grouting pile
(3) Pile forming detection
1) The detection method and the content high-pressure jet grouting can be used for detection by adopting methods such as excavation inspection, coring and unconfined compressive strength inspection, standard penetration test, load test and the like according to engineering requirements and construction experience.
And (3) inspecting the construction quality of the rotary jet grouting pile, wherein 28 days after the high-pressure jet grouting is finished, the inspection contents are mainly as follows: pile strength, average diameter, pile body center position, pile body uniformity and the like.
2) The number of detection points and the number of part inspection points are determined according to the design, and the standard generally requires that the number of the construction holes is 2 percent and not less than 5 points. The check points are arranged as follows:
firstly, representing pile positions;
secondly, the part with abnormal conditions in the construction process;
and thirdly, the foundation condition is complex, and the high-pressure injection grouting quality is possibly affected. And (5) carrying out supplementary spraying on the unqualified detected people.
3) The inspection standards for inspecting the construction quality of the standard high-pressure jet grouting pile are shown in table 2.
TABLE 2 inspection Standard of construction quality of high-pressure jet grouting pile
2. Double-liquid grouting
(1) Material and apparatus
1) Materials: P.O 42.5.5 Portland cement;
2) auxiliary materials: water glass 42Be DEG and an acidic admixture;
3) drilling equipment: a crawler-type hydraulic drilling machine;
4) grouting equipment: a static pressure grouting machine and a matched grouting pipe;
5) pulping equipment: a cement stirring barrel and a stirrer;
6) auxiliary equipment: flow meters, hydraulic tube extractors, slurry densitometers, and the like.
(2) Construction process flow
1) The working face is arranged on the excavated part of the earthwork, and C15 concrete with the thickness of 20cm is poured to serve as a grouting working platform.
2) The hole site arrangement is made clear on the hardened concrete by red self-spraying paint, the synchronous grouting hole sites are arranged according to the interval of 1m, and the arrangement of the synchronous grouting hole sites is schematically shown in figure 7.
3) The purpose of drilling during drilling construction is to smoothly place the grouting pipe into a preset position, drill a hole by a crawler-type self-propelled drilling machine, drill the hole to the depth of 8m below the elevation of the bottom plate bottom, and lift the drilling machine after drilling to the designed elevation. And drilling with water in the drilling process, measuring and correcting the hole inclination in the drilling process when the deviation of the hole verticality is less than or equal to 1 degree to ensure the hole verticality, reporting the acceptance of field management personnel of a project department after the hole drilling is finished, and entering the next procedure for construction after the acceptance is qualified.
4) The double pipe is laid after the grouting pipe is placed to the hole site and is qualified through inspection, the diameter of the grouting pipe is 42mm, and the top of the grouting pipe is wound by cotton cloth and plastic cloth after the pipeline is placed, so that the clearance between the grouting pipe and a drilled hole is reduced, and the slurry leakage is prevented. And the effective injection of the slurry is ensured, and the sealing rubber ring is checked during the pipeline installation. And installing the tube extractor after the placement is finished.
5) Slurry preparation
1) The slurry material consisted of P.O 42.5.5 type Portland cement, water glass 42Be °, and additives (phosphoric and sulfuric acids). See table 3 for specific parameters.
TABLE 3 back cover slip casting parameter table
Firstly, the residual caking in a stirring barrel is cleaned before the A liquid (cement slurry) is prepared and mixed,then adding water into the barrel, pouring cement into the barrel, and measuring the diameter of the first stirring barrel to be 1m, the height to be 0.75m and the effective capacity to be 0.5m according to the actual measurement on site36 bags of cement are added to mix a barrel of cement paste for 1m3The slurry requires 12 bags of cement to be put in. The second stirring barrel has a diameter of 0.8m, a height of 0.8m and an effective capacity of 0.33m34 bags of cement are added to mix a barrel of cement paste for 1m3The slurry requires 12 bags of cement to be put in. The cement paste after being stirred is required to have a water cement ratio of 1.3-1.35: 1 and a specific gravity of 1.41-1.42.
The method comprises the following steps of adding raw materials into a stirring barrel, starting a stirrer to stir for 10-20 minutes, then unscrewing a valve at the bottom of the stirring barrel, pumping a filter screen (with the aperture of 0.5mm) through a slurry pump, filtering, flowing into a slurry barrel, and standing by when grouting.
② preparing liquid B (water glass), diluting the water glass primary pulp into 35Be DEG, actually measuring the height of a stirring barrel at 0.9m, the diameter of the stirring barrel at 0.55m and the effective capacity of the stirring barrel at 0.2m on site3The dilution ratio is 1:1 (volume ratio), and 0.1m is required to be used for stirring a barrel of water glass slurry3Adding water 0.1m3Water glass.
Thirdly, the C liquid (additive) is prepared by adopting phosphoric acid or sulfuric acid, and the actual measurement on site is that the height of a stirring barrel is 0.9m, the diameter is 0.55m, the effective capacity is 0.2m3The dilution ratio is 9:1 (volume ratio), and 180L of water and 20L of acid are needed for stirring a barrel of additive slurry.
2) During grouting, the mode of mixing and injecting two kinds of grout is adopted for grouting
Firstly, mixing the chemical pulp with the liquid B and the liquid C in a ratio of 1:1, and allowing the gelling time to be 3-10 s;
and secondly, the double-liquid-slurry mixture ratio is that the liquid A and the liquid B are mixed in a ratio of 1:1, and the gelling time is 30-90 s.
6) Grouting
1) Before the formal grouting is prepared before grouting, the pipeline connection of all parts of the grouting system is checked to be normal, then the grouting pump is started to carry out a water pressing test, the connection condition of the grouting system is checked to have leakage, and the conditions of all surfaces of the grouting pump are checked to ensure that the pipelines are smooth and all instruments work normally. The grouting pressure is not more than 3.0Mpa, and grouting construction is carried out after the test is normal.
2) The grouting parameter is 1-3 Mpa, and the grouting pressure is not more than 3 Mpa. The flow rate of the slurry is 20-40L/min, and is not more than 40L/min.
7) And (3) adopting an alternate grouting mode during grouting construction, simultaneously grouting 4-8 holes, enabling two sides of each hole to correspond to each other, simultaneously and synchronously grouting in the same position as much as possible, firstly injecting 50-80L of chemical grout when grouting is started, then injecting 50-80L of double-liquid grout, and repeating the steps in the same way to perform circular construction.
And the grouting amount and the grouting pressure are strictly controlled in the grouting process, so that the balance and synchronization are ensured, the grouting pressure is observed through a flowmeter, and the pressure change condition along with the increase of the grouting amount is checked. And (3) controlling the pressure in the grouting process, when the grouting pressure reaches 2.0Mpa, lifting the guniting pipe by 0.2-0.5 m, continuing grouting, and repeating the construction until the construction is lifted to the designed elevation.
8) And sealing holes by using thick cement paste with the ratio of 0.8:1, and then leveling.
(3) Standard of end of grouting
1) And (5) finishing grouting standard: and (3) gradually increasing the pump pressure at the end of grouting construction, and when the grouting amount is less than 20L/min, continuously stabilizing for 15min after the reading of the pressure gauge is stably more than 2.5 Mpa.
2) And if a large amount of slurry returns in the grouting process, gradually reducing the grouting pressure, stopping grouting, grouting other holes, and returning to the hole position for secondary grouting after the grouting of the rest hole positions is finished.
3) And reporting to a field manager for inspection after single-hole grouting is finished, and plugging the hole site after the completion of the single-hole grouting is confirmed by the field manager.
The technological process of double-liquid grouting in bottom sealing construction is shown in figure 8, and the arrangement of a grouting system is shown in figure 9.
The above detailed description is of specific embodiments and should not be used to limit the scope of the claims.
Claims (3)
1. An HPPG back cover construction method comprises the following steps:
a) determining a deeper back cover construction depth according to the depth of the designed foundation pit;
b) determining that the design diameter D of the consolidated body at the construction depth of the back cover is not less than 600 mm;
c) determining the arrangement distribution of the consolidation bodies on the back cover construction depth plane, and forming a generally close-packed hexagonal or quincunx array which is mutually occluded with each other;
d) punching the bottom layer according to the determined arrangement distribution of the consolidated bodies until the construction depth of the back cover;
e) at the bottom sealing construction depth, carrying out rotary spraying on the stratum by using compressed air and high-pressure cement slurry to form mixed cement slurry of cement slurry and soil slurry with the diameter not less than D; a triple pipe method is used as a pile forming means in the rotary spraying process;
the technical parameters of the triple tube method are as follows:
simultaneously, high-pressure air rotary spraying is carried out, the hydraulic pressure of the cement slurry is not less than 0.2MPa, the specific gravity of the slurry is 1.60-1.80 ton/m 3, the pressure of compressed air is not less than 0.5MPa, and the pressure of high-pressure water is not less than 30 MPa;
the centers of three adjacent concretion bodies form the top of a regular triangle, and the side length of the regular triangle is 0.7-0.8D; the height of the cement soil pile formed by rotary spraying is not less than 100 cm, and the compressive strength is not lower than 1.0 MPa;
f) preparing slurry for static grouting:
the liquid A is cement paste, the water-cement ratio of the stirred cement paste reaches 1.3-1.35: 1, and the specific gravity of the cement paste is 1.41-1.42;
secondly, preparing a solution B which is water glass, diluting the raw water glass stock to 35Be DEG, wherein the volume ratio of the water to the water glass is 1: 1;
thirdly, the liquid C is used as an additive, phosphoric acid or sulfuric acid is used for preparing the additive, and the volume ratio of water to the additive is 9: 1;
2) during grouting, grouting is carried out by adopting a mode of mixing and injecting two kinds of grout, wherein the two kinds of grout are respectively chemical grout and double grout:
firstly, mixing the chemical pulp with the liquid B and the liquid C in a ratio of 1:1, and allowing the gelling time to be 3-10 s;
secondly, the double-liquid-slurry mixture ratio is that the liquid A and the liquid B are mixed in a ratio of 1:1, and the gelling time is 30-90 s;
g) performing static grouting in the range of the back cover of the jet grouting pile,
1) grouting parameters including grouting pressure of 1-3 Mpa and slurry flow of 20-40L/min;
2) in the grouting construction, an alternate grouting mode is adopted, 4-8 holes are simultaneously grouted, the distance between every two adjacent holes is 1m, the two sides of each hole correspond to each other, synchronous in-situ grouting is achieved, 50-80L of chemical grout is firstly injected when grouting is started, then 50-80L of double-liquid grout is injected, and the rest is done in the same way, and circular construction is carried out;
the grouting amount and the grouting pressure are strictly controlled in the grouting process to ensure balanced synchronization, the grouting pressure is observed through a flowmeter, and the pressure change condition along with the increase of the grouting amount is checked; adopting pressure control in the grouting process, when the grouting pressure reaches 2.0Mpa, lifting the guniting pipe by 0.2-0.5 m, continuing grouting, and repeating the construction until the grouting pipe is lifted to the designed elevation; and (5) finishing grouting standard: in the final stage of grouting construction, the pump pressure is gradually increased, and when the grouting amount is less than 20L/min, the pressure gauge reading is stably greater than 2.5Mpa, and then grouting is continuously stabilized for 15min and is finished;
h) sealing holes by adopting cement paste, and then leveling;
the double-liquid grouting method comprises the following specific steps:
1) arranging a working surface, and pouring C15 concrete with the thickness of 20cm on the excavated part of the earthwork to serve as a grouting working platform;
2) hole position arrangement, namely, marking the pile position clearly on the hardened concrete by using red self-spraying paint, and arranging synchronous grouting hole positions according to the interval of 1 m;
3) drilling, wherein the purpose of drilling is to smoothly place the grouting pipe into a preset position, the hole is drilled by a crawler-type self-propelled drilling machine, the hole depth is required to be drilled to 8m below the bottom elevation of the bottom plate, and the drilling machine is lifted after the hole is drilled to the designed elevation; drilling with water in the drilling process, wherein the deviation of the verticality in the hole is less than or equal to 1 degree, measuring and correcting the hole inclination in the drilling process to ensure the verticality of the drilled hole, reporting the acceptance of field management personnel of a project department after the drilling is finished, and entering the next procedure for construction after the acceptance is qualified;
4) the slip casting pipe is laid the hole site and is laid dual pipe after passing the acceptance inspection is qualified, slip casting pipe diameter 42mm, and the pipeline is laid the back and is twined slip casting pipe top with cotton and plastic sheeting, reduces the clearance of slip casting pipe and drilling, prevents to run the thick liquid and leak the thick liquid, ensures the effective injection of thick liquid, will inspect sealed rubber ring in the pipeline is laid, lays and will pull out the pipe ware installation after accomplishing.
2. The HPPG back cover construction method according to claim 1, wherein in step e), the jet grouting rotation speed is not less than 20 r/min.
3. The HPPG back cover construction method according to claim 1, wherein in step e), D is equal to 800mm, and the side length of the regular triangle is 600 mm.
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